Bangkok, Thailand (CNN) -- Sixteen insurgents were killed during a fierce battle after they attacked a military base in a restive area of southern Thailand early Wednesday, authorities said.
Thai military officials said 50 to 60 heavily armed attackers tried to storm the navy base in the province of Narathiwat under cover of darkness, but navy personnel had been forewarned and fought the insurgents off in an intense, hour-long firefight.
It appeared to be the latest flare-up in a worsening conflict between government forces and Muslim separatists in southern Thailand in which more than 5,000 people are believed to have been killed since 2004.
Although Thailand's population is overwhelmingly Buddhist, Muslims make up a large percentage of the population in the country's three southernmost provinces, near the border with Malaysia.
Parts of those provinces have been under an emergency security decree for years, but analysts say the Thai military is struggling to deal with the militants.
"Insurgents have withstood and adapted to the military's tactics, growing more proficient and daring in the process," the International Crisis Group, a nonprofit organization that provides analysis and advocacy on conflicts around the world, said in December.
Meanwhile, successive Thai governments "have opted to muddle through South East Asia's most violent internal conflict," the group said in a report on the conflict, citing "bureaucratic turf battles and a bitter national-level political struggle."
The insurgents who carried out the attack Wednesday were armed with military-grade weapons, including laser-guided rifles and hand grenades, said Col. Pramote Promin, a spokesman for the Thai military.
Some of the roughly 100 Thai navy personnel on the base were wounded in the fighting, he said, but none were killed. The military had received a tip about the attack and was "on full alert" when it happened, he added.
The military is now trying to track down wounded insurgents who fled from the clash, Pramote said after visiting the area.
He said that after a count at the base, the number of insurgents killed stood at 16, one fewer than the initial total he gave earlier Wednesday.
There was no word Wednesday from the elusive Muslim separatists, who don't usually claim responsibility for attacks they carry out.
Unrest linked to arrest
On Sunday, a roadside bomb in Yala province, which is next to Narathiwat, killed five Thai soldiers, authorities said.
Lt. Gen. Dithaporn Sasasmit, a spokesman for the Thai internal security operations command, said recently that the latest insurgent violence is related to the arrest of one of the separatist leaders in January.
"Every time when authorities can arrest or conduct raid operations to prevent possible attacks, they would try to show off and create some situations," Sasasmit said.
Human Rights Watch last year said that in 2011, insurgent groups targeted teachers they saw as symbols of state efforts to undermine Malay Muslim identity. The group said that Thai security forces have faced few consequences for abuses against Muslims.